The invention is directed to a combine with a novel short-wave U.V. excited, (herein, short-wave U.V. is defined as U.V. light having a wavelength of 300 nm or less) fluorescence sensor used to detect levels of damage in grains or seeds, including but not limited to cracked or broken conditions in the grain or biological contamination. This sensor can be used on grain that is in either a stationary or a moving state, and therefore is used in an operating combine harvester (hereinafter combine), for example in a grain elevator for quality control. Hereinafter, the sensor will be referred to as either a cracked grain sensor or simply a sensor.
The prior art suggests the desirability of having an effective method for detecting grain which has been mechanically damaged, or cracked. Many of the methods which have been hitherto developed are only usable in a laboratory setting, and are not adaptable to real-time use in a combine.
Some methods require that a chemical solution be applied to the grain (U.S. Pat. Nos. 4,000,975 and 4,020,682), which can render such grain harmful for human or animal consumption. Other methods require undue destructive sample preparation (U.S. Pat. No. 4,000,975), which precludes the use of those methods for real-time detection of damaged grain kernels in a continuous flow of grain material.
U.S. Pat. No. 4,572,666 discloses a through-beam method for the detection of cracked rice, in which a coherent light beam is passed through individual rice grains. Such a method is limited to grain of a translucent nature and can only be used with small quantities of grain, such as in a laboratory setting.
U.S. Pat. No. 4,348,855 proposes an arrangement of sieves and impact transducers (similar to those used for grain loss monitoring) to separate and detect damaged grain inside a combine. However, this method does not adequately discriminate between small but intact grain kernels versus pieces of debris and broken pieces of larger grain kernels.
Infrared and near-infrared methods such as described in U.S. Pat. Nos. 5,132,538, 4,806,764, and 5,751,421 are used primarily to determine the constituents of grain, such as oil, protein, starch, and moisture and are not intended for damage detection. Likewise, U.S. Pat. No. 4,421,772, which uses a range of visible, ultraviolet and/or X-ray radiation to determine characteristic fluorescence from the component parts of ground seeds and other botanical matter, is not targeted for grain damage detection. However, this patent teaches the use of short-wave UV as an optimum excitation wavelength for the detection of fluorescence emission related to the starchy endosperm of grains.
Other methods use either machine vision under visible light (see xe2x80x9cImage Processing and Neural Networks Classify Complex Defectsxe2x80x9d by Wilson, in Vision Systems Design, March, 1999) or machine vision augmented with long-wave UV light (U.S. Pat. No. 4,713,781) Machine vision requires expensive imaging components, such as CCD cameras, artificial illumination, and complex signal processing means. Despite progress in the performance of machine vision systems, the complexity of the task does not allow for processing speeds essential to real-time applications. Also, the use of a CCD camera dictates the selection of long-wave UV excitation, rather than the more effective short-wave UV excitation, thereby impairing the capability of accurately determining the presence of damaged grain, because more background light from the source reaches the detector.
A first object of the present invention is to provide an apparatus for detecting levels of damage in grains or seeds, including but not limited to cracked or broken conditions in the grain. A second object of the present invention is to provide a short-wave U.V. excited fluorescence sensor which will detect levels of damage in grains or seeds in a fast, accurate, and consistent manner. A third object of the present invention is to provide a damaged grain sensor applicable to grain that is in either a stationary or a moving state, and therefore the sensor can be used in an operating combine, in a grain elevator for quality control, or as a hand held detecting device.
These and other objectives are achieved by the present invention, which includes an ultraviolet light source that provides a certain short-wave UV excitation wavelength (e.g., 253.6 nm) to which the grain is exposed. Different constituents of grain emit different levels of fluorescence. The endosperm of grain, when exposed to said certain excitation wavelength will fluoresce at a certain emission wavelength (e.g., 335 nm) with a substantially higher intensity than will the pericarp, or hull of the grain. Therefore, if grain has been damaged, such that the grain has been cracked or broken so as to expose the endosperm, a measurable difference in fluorescence intensity can be detected between the damaged and undamaged states of the grain by using a non-imaging photon detector. Other elements of the invention are present in order to concentrate the desired fluorescence signal on the non-imaging photon detector and to process the signal from the photon detector.
The present invention is advantageous as compared to the prior art in that the sample is not exposed to chemicals. Nor is undue preparation of the sample or destruction of the sample required. The present invention can be used with a wide variety of grain types and is not reliant upon through-beam illumination, which is unsuitable for high volume flow as well as for measuring damage to grains that are not translucent. Because the present invention does not rely on imaging of the sample onto the detector, optical components that may be used to gather light in order to concentrate the luminescence onto the detector can be inexpensive. Further, the complexity of signal processing is drastically reduced and the signal processing time is shortened so that real-time measurement applications are feasible. Additionally, the present invention allows the use of more effective, short-wave UV radiation for fluorescence excitation, which minimizes the detection of false signals. For the above reasons the apparatus of the present invention may be built of standard electronic and optical components that are available at low cost.